1. Field of the Invention
The present invention relates to an RFID tag, and more particularly to an RFID tag having capacitive load.
2. Description of the Related Art
RFID (Radio frequency Identification) tags are directly attached to products, so it will encounter many problems during application. In conventional technology, the system cannot read the identification information in RFID tags in the case of, for example, products packaged with metal material, products with liquid content and so on. Especially in application with metal items, as metal is an ideal conductor and a perfect reflecting surface for electromagnetic waves, interference with signals often occurs when RFID tags are attached to metal items, and antennas close to the metal items cannot effectively receive and transmit electromagnetic waves; as a result, the effective reading distance of the system is decreased from meters to 1-2 centimeters, or the system totally fails.
In order to apply RFID technology to metal items such as automotive components, containers, industrial equipment and so on, specialized RFID tags have been developed, but such RFID tags in conventional technology are too big in size and costly. Therefore, developing specialized RFID tags for use with metal which are small and cost-efficient is a goal that has not yet been achieved.
Moreover, recent development in RFID technology is toward item-level, so miniaturization is desirable in the design of RFID tags. In conventional design of RFID tags at item-level, providing the necessary inductive reactance is the main purpose, and this conductive design totally depends on the length of a current loop; because of the limitation by physical characteristics, highly inductive tag antennas are relatively large in size, which goes against the requirement for further miniaturization.
Therefore, it is necessary to provide an RFID tag having capacitive load to solve the above problems.